Choke with contacting finger and sleeve surfaces of concentric arcs



April 4, 1961 E. SCHACHT 2,977,702 CHOKE WITH CONTACTING FINGER ANDSLEEVE SURFACES OF CONCENTRIC ARCS Filed June 8, 1954 FICEZ IN VEN TOR.Emma Same/1r Arm/ways ment of the sleeve.

l atented Apr. 4, 1961 vices, frequently referred to as variable chokes,normally comprise a tubular shell member fixed to the barrel andhaving'a forward portion adapted to be contracted and expanded to varythe bore diameter of the muzzle end of the barrel. The shell has aplurality of annularly arranged resilient wall segments at its forwardend with an adjusting sleeve around the segments for opening or closingthe same relative to each other. ,This is conventionally eflected byforwardly taperingthe outer surfaces of the segments and providingatapered mating surface on the sleeve interior sothat contraction andexpansion of the choke opening is controlled by longitudinal move-Examples'of this construction are very common in the art. r I

In conventional chokes using the tapered shell such as above mentionedit is necessary that the adjusting sleeve engage the shell segments onlyalong their extended end portions leaving a space between the sleeve andthe se gments along their inner portions. So constructed the segments donot have adequate backing and become distorted in time rendering theshell ineffective for governing the shot pattern.

' 'Where the tapered shell and cooperating sleeve are used a'fullbacking of the segments by the sleeve proves inoperative; This is due tothe fact that when the sleeve is adjusted inwardly to close the chokethe sleeve will exert inward radial pressure only upon theinner= orrearward portions-of the forwardly extending shell segments leavingtheir extendedends contracted to a position where they arespacedinwardly from ahdunb'acke'd by the adjustment sleeve. This is dueto the fact that the -straight taper'will attempt to move each segmentinwardly the same distance along its entire length'while the shellconstruction demands thatto bringaboutthe choke the extended or forwardend portions of the seg- 'ments' must; s V 7 than ;the'i'nner "orrearward portions thereof.

move radially inward a greater distance x'Forth'ese reasons, heretoforeknown variable choke constructions have failed to provide for rigidshell segthe ctive"nece'ssitatingrepair J I: V s accordinglyv theprimary object ofmy invention f'to --provide an 'irnpi'ove'd adjustablefchoke construct kin" gr ri'shetguns whereiii' ,the segmentsofthe chokeshell'will "have-complete and adequate-backingregardless of the j1adjustmentgofthe chokeopening; i

.-...Another.. object of the invention? is-topmvide ia ishot patterncontrol device; for shotgunswhich will-maintain durable and yet which issimple in design allowing its manufacture at a relatively low cost.

With the above mentioned objectives in mind, my invention broadlycomprises forming the exterior surface of the choke shell segments tocurve longitudinally inward toward the forward end thereof, said curvebeing the arc of a circle, and the interior of the adjustmentsleevehaving a mating curved surface in flush engagement with said exteriorsurface of the shell whereby as the sleeve is adjusted longitudinally onthe shell the seg ments will be constantly backed throughout theirlength bythe sleeve.

The above mentioned and still additionalobjects will be brought to lightduring the course of the following specification, reference being madeto the accompanying drawing, in which:

Fig. 1 is a top plan view of my improved shot pattern control devicefixed on the end of a shotgun barrel.

Fig. 2 is a longitudinal section of the device taken on line 2-2 of Fig.1 and showing the choke shell in fully open condition.

' Fig. 3 is a longitudinal section similiar to Fig. 2 with the chokeshell in contracted or full choke condition.

Fig. 4 is a transverse section taken on Knee-4 of Fig.2. a

Referring now more particularly to the drawing, reference'numerals willbe used to denote like parts or structural features in the differentviews. The muzzle or discharge end of a shotgun barrel is designatedbythe number 5. I have shown my improved shot pattern control devicemounted on the barrel end 5, though it is possible to form the shellmember, denoted generally at 6, of the device integral with the barrelif desired. The shell 6 is of generally tubular shape and is fixed t0the barrel in axial'alignment therewith in. any suitable detail. It hasa coller' 10 at its inner or rear end adapted of the shell.

manner as by soldering or screw threading. The numher 7 indicatesgenerally a cylindrical adjustment sleeve which fits around the sleeve 6and which isconnected thereto by suitable means, to be later. described,allowing the sleeve to be longitudinallyadjusted thereon.

In Fig 'l .there is shown a compensator of sleeve 8 7 threaded on theforward end of sleeve 7." This cornpensator 8 provides a conventionalexpansion chamber" at the forward end ofthe gun barreland has a seriesof slots 9 therein to allow: escape of the expanding gases following theI discharged shot mass. [he member -S forms no part of thepresenhinvention and is tf'shown merely as exemplary of a mannerin whichthis desirable feature can be employed in connection with th'el'n ovelchoke device hereindisclosed. 1

The inner .shell ,6 will now be described in greater to fit: snuglyaronntl the barrel fopattaizhment thereto. 1 Forward ofthe collar 10 theshell has'a. reduced internal diameter which is. equalto that of the gunbarrel bore.

There is a solid annular portion 11' disposedbetweien the collar, 10 andthe forwardconstrictable choke portion 12/ I u Choke portion 12haslongitudinal slots 14 extending rearwardly from the forward. end {oftheshell which divide the portion 12"intoj a plurality'of annularlyarranged forwardly extending segmentsa or fingers'15. Therear end of theichokeportion 12' is fprovided with' a peripheral r v '0 ts accuracywithout repair throughout long periods of I I'us "-2 external channel"or groove 13, thepnrpose of which is to reduce thethickness oftheshellwall at at pai 1'9 OW- he e ment .15 o resiliently" e ed seat 19,the threads 17. and fIQbeing in screwthreadf ling. fil jgcmcut with ieach oth er This rnean'sf allows ftotation of the 'slecvfeon thcjshellfor, longitudinal adjust- I i them.- Slits 14 ann al-any :wide: to new alimited I amount of such radial movenicntofall of the segments i z'simultaneously for contraction of; the choke .portion of;

i i h l-- -:"'I I i l The external contour of the choke portion ,12 andthe f I 3 I 1 segments 15, which compose th a; same is of critical int-1I I I portance to the present invention. The external surface f of theportion; 12;ftom the. channel; 13 on forward fisf I denoted by the;numerfalj :16; 3 This surface is round in I i transverse cross sectionon any such section along its;

' entire; length, fThejfore. and an contour; of the: surface I I Ipreferably nearthe'transversewertical plane of the reef end; of the.surface; 16. The longitudinal curve is, very gradual; as shown, andpreferably; although not 'neces I 1 I f eer ly; comprises le s than tendegrees or the ifi l 1 33i r I i The'sheil (i is externally threaded as;at 17 Eat a place I to the rear; of the contractible portion :12. Therear; end.

' I portion18of the adjustment sleeve 7 ijsiinternaliy'thread j I f tiv'e shot; pattcrn control device for. carryingfout the aforei mentionedgobjectiv .modifications may; be made in the structure ajsgdisclosed;

i ment of the former.- The sleeve 7 may be provided'wit l 1 I 1 1111 Ptia k ur dsurf -ace 29tojfacilrtat 1fts manual m-f tfion.

: i i The ifcir wafrd portion of I sleeve IT forms a wag n I l .means;and 'sjdesignatedj by the: number ZZandi the; front I f I Een'd thereofis: reduced as at 23 and threaded for attachment of the aforementionedcompensator 8.; Theintefrior I I surface; 24., of the sleeve portion 2:2is contoured to mate- I with the surfaceiltiiof'the shell 6. 1 The;surface is accordiingly. concave being round 1 in; cross section.{throughoutits length and longitudinally curviug I inward, on are 1 I Ij having the same center} as that of; the longitudinal are I I i jdescribed by thefimmediateiyadjaeentsurface 16. it is I f j desirableithat the sleeve '7' and its intejri'or surface 24. I j extend .forw ar;ly a slight distance? beyond the 'shellf 6 i when the ch'okeisi in'opehposition as s'hown in Fig 2.=

The operation of the device will now be clearly understood. When thesleeve 7 is in its forward position (Fig. 2) the internal diameter ofthe shell or choke tube 6 is constant throughout its length, a diameterequal to the bore of barrel 5. The choke is then in open condition andeach segment has complete exterior backing throughout its length by thesleeve portion 22.

To bring the device to a full choke the sleeve 7 is rotated to moveinwardly on threads 17 and the portion 22 becomes a wedge with surface24 exerting radial pressure upon the surface 16. Segments 15 will yieldinwardly to bring the shell portion 12 to the contracted condition shownin Fig. 3. The pitch of threads 17 and 19 is preferably coordinated withthe-shell contour whereby the segments are brought to a full chokeposition upon one complete revolution of the adjustment sleeve.Obviously the choke opening may be varied by adjusting the sleeve lessthan one revolution as desired. An indicator scale may be provided onthe collarltl or sleeve portion 18 to aid in proper adjustment.

In adjusting the choke, surface 2,4 will slide flush along the surface16 giving complete backing atall positions. Segments 15 resilientlyyield primarily at their reduced wall portion 13. When the segments areplaced under inward pressure the extended ends of the segments willobviously be moved inwardly. a greater distance than will the rearwardor attached portionsthereof) Thus the shot blasts. 1 This, ream-reobviously renders the choke 5 backing of the. fingers is lacking,-the-ref .is a smallerarea I 5 of engagement between. the choke tube andthe wedzg'ing I I 3 1 Accordingly there I 3 f greater longitudinallyinward pitch of the surface 16 near its extended end is completelycompensated for by 1 the like pitch of the forward end area of surface24.

My invention has two primary advantages which .will

be readily understood. First withthe segments or fingers having uniformand complete backing throughout their length whether in open, fullchoke, or any position therebetween, they will not become deformedunderrepeated surface 5 of the adjustment sleevel mustbe considerablepressure exerted. at these small I I 1 areas of contact; I This makesrotation of the adjustment :I I I 16 onany diametricalbr longitudinalsection of} the choke j i sleeve more difficult than in the: presentconstruction. I Q Portion 12 i moves on an are which: curves inwardly In.rny improved: device the :wedging pressure I is exerted I in itsforwardprogfression; This are has its center located I i I Both; ofthese advantages are direct result. of the: 5 I exterior longitudinal:contour of the; forward slotted ;po'r- I I I I tion .of thej shell andthe; mating: interior contourofthe 5 20,

haveaccordinglygprovided an; economical and efEecZ- adjustment sleeve.-

lt is under t od that, suitable provided such modifications icotnewithin the :spirit and j y f 1 scope of} the appended claims; Havingnolwl therefore; I a j I I fully illustrated and described myinventionwliat Iclairnf I to be new and; desire to protect: by LettersPatent is: r 5 I I I i 11; .Infa; shot pattern control device for ashotgun-, a 1 j i generally: tubular: shell {for mounting on the}fotwardiend I I j of the gunjbarrel and in axialaligriment therewith;said I j I-Sl1ell having a plurality of; annularly spaced slits in; the;I i wall thereof extending; longitudinally rearwardlv from its front endso as to: divide-the-wallinto a series of forilwardlyg extendingfingers'radially contract'able grinder pe-. ripheral pressure toconstrict the passage 5 through; the f forward end portion of the shell;a sleeve; encircling the I shell% and secured thereon itor; longitudinaladi sim I I with respect thereto, said sleeve-having ianfannular n 1' isurface in peripheral pressure contact with the; outer j i surfaces ofsaid fingers and throughout substantially the entire lengths thereof,the outer surface of each finger and the inner surface of the sleeve incontact therewith being contoured in a longitudinal direction to followthe curves of concentric arcs, whereby when the sleeve is longitudinallyadjusted on the shell the said inner surfaces thereof will continue tomaintain contact with the outer surfaces of the fingers throughoutsubstantially the entire lengths of the latter. I

2. A device as described in claim 1 in which the rear ends of thefingers are integrally united with the rear part of the shell by reducedneck portions adapted to bend when the fingers are contracted under thepres sure applied by the sleeve. I

3. In a shot pattern control device for a shotgun, a generally tubularshell adapted to be mounted on the muzzle end of the shotgun barrel andin axial alignment therewith, said shell having an externally threadedrear portion and a choke portion forward of the threaded portion, anadjustment sleeve encircling the shell and having internalthreadscooperating with the rear portion of the shell forlongitudinaladjunstment of the sleeve on the shell, the wall of thechoke portion of the shell having ;a plurality of slots extendinglongitudinally rearward from the forward end thereof to divide saidportion into a plurality of annually arranged forwardly extendingsegments adapted to have their forward ends moved radially .inwardly toconstrict the passage through the choke portion, said choke portionhaving an external surface which is circular in cross sectionatlanypoint throughout its entire length, the outer surfaceof each ofsaid sections andthe inner surface of the sleeve immediately adjacentthereto being longitudinally curved in concentric arcs.

(References on following page) boith accurate and inexpensive to ioperate over extended; I I l I .pe riods.ofuse r Second primar featureof any impr h k @5114 I structi'onlie's in the ease and. speed withwhich it m y b5 i I I i manually adjusted. .In conventionai chokesiwlzlere f i I I 5 unili'or'rnj'ly' over the entireouterisjurface of thefingerpot I tion or. the choke allowing the choke @device. to} be ;ad 5I Q justed with relative ease. i i i 5 References Cited in the file ofthis patent 1,892,522 2,153,246 V UNITED STATES PATENTS 2,490,8291,348,750 Schuster Aug. 3, 1920 2,629,958 1,508,605 Legett et a1 Sept.16, 1924 5 2,676,429

6 White Dec. 27, 1932 Gibson Apr. 4, 1939 N011 Dec. 13, 1949 Roper eta1. Mar. 3, 1953 Gotterson Apr. 27, 1954

